Vehicle seats typically include a generally horizontal seat bottom and a generally upright seat back. Vehicle occupants are seated on the seat bottom, which normally includes cushioning for comfort. The seat back may also include cushioning for comfort, but because of the upright position of the seat back, the occupant's weight is not always useful to ensure a comfortable, conforming fit of the seat back with the occupant's body. Further, not all vehicle occupants sit with the same posture. Some occupants sit in a relatively upright position, while others may sit in a slumping position. These different postures place parts of the occupant's body in different physical locations from each other. Thus, a seat back with a fixed shape or contour is likely to properly fit and support only a small portion of possible occupants. While some seat backs are constructed with a user selectable contour, there are typically only a finite number of contours to select from, which may or may not be suitable for a particular occupant. In addition, an occupant may shift in his or her seat from time to time. This shifting can resulting in changes in posture so that even a properly adjusted seat back contour becomes improper without additional adjustment to suit the occupant's shifted position.